Apparatus for imitating great values of electric resistance

ABSTRACT

An apparatus for imitating a great value of electric resistance is disclosed, which can be connected to an instrument to be tested, having a set of input terminals of any kind, this apparatus comprising at least three resistors connected into a star circuit and mounted inside an electrically conductive housing, this apparatus further comprising an auxiliary housing disposed inside the main one, the auxiliary housing includes a closed electrically conductive body receiving said at least three resistors thereinside; that one of the radii of the star circuit, which has the electric resistance lower than that of the other radii, is connected to the body of the auxiliary housing; the apparatus further comprises at least three outgoing electrical conductors one of these conductors is electrically connected with the body of the auxiliary housing and the other two conductors extend through separate insulating members mounted on the body of the auxiliary housing.

United States Patent Inventors Anatoly Mirouovich Cllerlov Bnelachenko l9, kv. 24; Vladimir Dmitrievich Kibenko, Kuznechny pereulok, 97, kv. l2, both of Kisllinev,

[LS-SR. Appl. No. 2,805 Filed Jan. 14, 1970 Patented. July 27, 197 l APPARATUS FOR IMI'IATING GREAT VALUES 0F ELECTRIC RESISTANCE 4/1967 Sauer 338/320 X Primary Examiner- Darrell L Clay Attorney-Waters, Roditi, Schwartz and Nissen ABSTRACT: An apparatus for imitating a great value of electric resistance is disclosed, which can be connected to an instrument to be tested, having a set of input terminals of any kind, this apparatus comprising at least three resistors connected into a star circuit and mounted inside an electrically conductive housing, this apparatus further comprising an auxiliary housing disposed inside the main one, the auxiliary housing includes a closed electrically conductive body receiving said at least three resistors thereinside; that one of the radii of the star circuit, which has the electric resistance lower than that of the other radii, is connected to the body of the auxiliary housing; the apparatus further comprises at least three outgoing electrical conductors one of these conductors is electrically connected with the body of the auxiliary housing and the other two conductors extend through separate insulating members mounted on the body of the auxiliary housing.

APPARATUS FOR IMITATING GREAT VALUES OF ELECTRIC RESISTANCE The present invention relates to apparatus adapted to effect measurement of electrical values, and, more particularly, it re latcs to apparatus for imitating great values of electric resistancc, which can be used, for example, for calibration of various instruments adapted to measure electric resistance.

There are known apparatus for imitating great values of electric resistance. In this known apparatus three resistors are connected into a star circuit and are mounted within a metal housing on electrically insulating mounting members. After having been electrically connected to an instrument to be tested, the resistors of the star circuit are released from their respective mountings, in order to eliminate current leakage through the insulation.

However, this known apparatus is not free from certain disadvantages, among which are on the one hand, a comparative complexity of the structure of the insulating mountings, which, as it has been explained, are adapted to release selectively the resistors of the star circuit and, on the other hand, the fact that this known apparatus can be connected only to those instruments which are provided with a special set of contact terminals.

It is, therefore, an object of the present invention to create an apparatus for imitating a great value of electric resistance, which should be adapted to be connected to instruments provided with any kind of input terminals, and which apparatus should further feature a relatively simple structure.

It is another object of the present invention to create an apparatus for imitating a great value of electric resistance, which should be adequately protected against current leakage through the insulation thereof and against a tendency to display a microphony response.

With these and other objects in view, the present invention resides in an apparatus for imitating a great value of electric resistance, comprising at least three resistors connected into a star circuit and mounted within an electrically conductive main housing, in which apparatus, according to the invention, there is provided an auxiliary housing including a substantially closed electrically conductive body mounted internally of said main housing and receiving thereinside said at least three resistors, one of the radii of said star circuit having a lower value of the electric resistance, than the other radii of said star circuit, said one radius being electrically connected to said body of said auxiliary housing, said apparatus further comprising at least three outgoing electric conductors, one of said outgoing electric conductors being electrically connected to said body of said auxiliary housing; two other ones of said at least three outgoing electric conductors being electrically connected to said star circuit and extending through the respective insulating members mounted on said body of said auxiliary housing.

In a preferred embodiment of the present invention said body of said auxiliary housing is of a substantially rigid structure, which provides an adequate protection against a tendency of said apparatus to display a microphony response.

The present invention will be better understood from the following detailed description of an embodiment thereof, with due reference being had to the accompanyingdrawing, showing a schematic circuit diagram of an apparatus for imitating a great value of electric resistance, constructed in accordance with the present invention.

Referring now in particular to the appended drawing, an apparatus for imitating great values of electric resistance comprises three resistors R R R which are star-connected to one anotheri The three resistors are mounted within an auxiliary housing 1 which latter has a closed hollow electrically conductive body, the three resistors being mounted thereinside in the following manner.

The resistor R which has the lowest ohmic resistance value of the three has its external, or free conductor connected to the auxiliary housing 1. The respective external, or free conductors of the two other resistors R and R extend through the respective separate insulating members 2 and are connected to the respective external terminals 3 of the apparatus. The third external terminal 4 of the apparatus 'is electrically connected to the auxiliary housing 1. t

The body of the auxiliary housing 1 is rigid; it is mounted internally of the external electrically conductive housing 6 on electrically insulating mountings 5.

The resistor R in a preferred embodiment of the present invention has an adjustable value of the electric resistance thereof, whereby it serves as a measure,'and the value of electric resistance, imitated by the herein disclosed apparatus can be controlled within a wide range.

The apparatus operates as follows.

It is known from the theory of electric circuits that when three resistors are connected into a star circuit, it becomes possible in the multipole circuit thus formed to obtain across a pair of poles a value of resistance which is many times greater than the inherent resistance of the respective radii of this star circuit, because when a star circuit is treated as an equivalent delta circuit, the respective values of the resistance of the sides thereof can be calculated according to the following formulas:

rz t 2 1' 2/ 3) |a 3+( i a/ 2) 23 2+ a+( z' 3/ r) where R R,;,, R are the respective values of the resistance of the three sides of the equivalent delta connection and R R R as it has been already mentioned, are the values of the electric resistance of the respective radii of the star circuit.

As it can be seen from the above formula, when two of the three resistors in the star connection have a relatively great value of electric resistance, whereas the third one is of a relatively small resistance value, as compared with the other two, then the resistance across the side of the delta connection, 0pposite to this third resistor, would be considerably greater than any one of the values of the resistance of the actual resistors. Let us presume that R,=R,-*-1O Ohm and The herein disclosed apparatus, embodying the invention, can be connected to an instrument being tested, having the terminal arrangement thereof of any kind; the abovedescribed mounting of the star circuit inside the auxiliary housing 1 provides for the resistance being imitated, i.e. for the resistance R of the equivalent delta circuit, being not shunted by the insulating members 2. The respective equivalent values of the resistance r," and r of these insulating members 2 are shunting the imitated resistance values R and R This, with the resistance of the insulating mem bers being about 10'' Ohm and the respective values of the R and R, being not in excess of 10"Ohm, means that the values of the R and R are effected by no more than 0.01 percent their nominal value. Electric resistors featuring the nominal resistance values thereof up to 10"Ohm are manufactured at present from a molded manganine microwire and invariably feature a high accuracy (within 10.05 percent), stability of performance and low temperature coefficient.

A major advantage of the herein disclosed apparatus, embodying the present invention, resides in the fact that when such apparatus is operated, it is not necessary for the instrument being tested to have a special set of terminals. Moreover, the low-ohmic radius of the star circuit can include a variable resistor, whereby the value of the resistance imitated can be controlled within a wide range. The apparatus is adequately protected against current leak through the insulating members thereof, as well as against a microphony response; it is structurally simple, which adds to the advantages offered by the present invention.

What We claim is:

I. An apparatus for imitating a great value of electric resistance, comprising at least three resistors connected into a star circuit, a main housing having said at least three resistors mounted thereinside; an auxiliary housing mounted within said main housing and having a substantially closed hollow electrically conductive body receiving thereinside said at least three resistors, said star circuit having one of the radii thereof having a lower value of electric resistance than the other radii of said star circuit, said one radii of said star circuit being electrically connected to said electrically conductive body of said auxiliary housing; electric insulating means mounted on said body of said housing; a plurality of outgoing electric conduc- 

1. An apparatus for imitating a great value of electric resistance, comprising at least three resistors connected into a star circuit, a main housing having said at least three resistors mounted thereinside; an auxiliary housing mounted within said main housing and having a substantially closed hollow electrically conductive body receiving thereinside said at least three resistors, said star circuit having one of the radii thereof having a lower value of electric resistance than the other radii of said star circuit, said one radii of said star circuit being electrically connected to said electrically conductive body of said auxiliary housing; electric insulating means mounted on said body of said housing; a plurality of outgoing electric conductors of said apparatus, one of said plurality of said outgoing conductors being electrically connected to said electrically conductive body of said housing, a pair of other ones of said plurality of outgoing electric conductors being electrically connected to said star circuit and extending through said insulating means.
 2. An apparatus, as set forth in claim 1, wherein said body of said auxiliary housing is of a substantially rigid structure, which provides an adequate protection against a tendency of such apparatus to display a capacitive microphony response. 